Thanks this was really useful. Looking at Unity I discovered is possible achieve the same effect using Amplify Shader.
Now I’m really near in obtaining what I need if I will be able to emit particles from the border texture.
Unfortunately this appear to be not possible neither in Unity, Unreal or CryEngine.
Considering Unreal this thread
state from official Unreal staff the feature will be available in the upcoming Niagara particle system (no way to know when will be released).
I can’t find another way to achieve it, maybe someone more experienced can have a different idea.